Abstract
We used a heart rate memory apparatus to measure 2047 successive R-R intervals with an accuracy of 10 msec in adult goats. For 100 successive stationary R-R intervals out of the 2047 intervals, the R-R intervals sequence was recorded graphically and the means and standard deviations (SD) were calculated. The magnitude of the variation in the R-R intervals was represented by the SD. The usefulness of the analysis of R-R intervals as an indicator of autonomic nervous activity was determined. The diagram of 100 successive R-R intervals at rest showed a conspicuous periodic fluctuation. After the administration of atropine, atropine plus propranolol or after feeding, the R-R intervals were markedly shortened and the variations in the R-R intervals were abolished. After the administration of propranolol only, the R-R intervals were prolonged and the amplitude of the fluctuations in the R-R intervals was conspicuously increased. The respiration curve and the variation in the R-R intervals at rest fluctuated in periodic synchrony. A positive correlation between the mean and the SD of the R-R intervals was highly significant. This indicates that the variations in the R-R intervals in the adult goats are closely related to autonomic nervous activity and that the analysis of the R-R intervals is suitable for the noninvasive assessment of autonomic nervous activity.
